Carburetor



Sept- 10, 1963 R. E. KALERT, JR., ETAL 3,103,544

CARBURETOR 2 Sheets-Sheet 1 Filed June 19, 1961 INVENTOR. RALPH E. KALERT JR. BYOLIN J. EICKMANN W AGENT Sept- 10, 1963 R. E. KALERT, JR., ETAL 3,103,544

CARBURETOR 2 sneets-sheef 2 Filed June 19. 1961 F I G. 7

Unted States Patent O 3,103,544 CARBURETOR Ralph E. Kalert, Jr., Granite City, Ill., and Oiin J. Eickmann, Normandy, Mo., assignors to ACF Industries,

Incorporated, New York, N.Y., a corporati'on of New Jersey Filed June 19, 1961, Ser. No. 113,125 9 Claims. (Cl. 261-41) This invention is directed to a fuel and air mixing valve for an internal combustion engine and is also adapted for use in a 'carburetor.

Mixing valves are basically tubular mixing conduits into which air and fuel are introduced and mixed before introduction into the intake manifold of an internal combustion engine. Such valves also include a suction tube which, when the mixing valve is attached to a :fuel source, extends into the fuel to provide a flow of the fuel into the m'ixin'g conduit. Such mixing valves 'are mounted directly :on the fuel tank of the engine and thus eliminates a special :carburetor and its required connections to a source of fuel and to the intake manifold. Mixin-g valves are normally less expensive to fabri'cate and are less complex in structure and are utilized with engines Where a definite cost reduction is desirable. Mixing valves, similarto carburetors, normally have a throttle valve 'mounted within the mixing con'dut for controlling the 'amount of air a'n'd fuel mixture introduced into the engine manifold, as well as a choke valve moun-ted within the mix-ing 'conduit to insure a rich fuel mixture for starting. Also, a restriction is formed within the mixing conduit to provide a -depression of atmospheric pressure within the mixing conduit to suck fuel upwardly through the suction tube and into the mixing conduit.

Mixing valves are normally less efiicient 'because of having minimum working parts 'and adjustments. One difiiculty in Operating mixin'g valves is the fact that, since they are mounted directly on the rfuel tank of the engine, the change in level of the fuel within the tank has an adverse effect. Since fuel is suckeid up through the suction tube into the mixing conduit, changes in fuel level` in the fuel tank vary the amount of 'fuel brought into the mixing conduit at different Operating speeds of the engine. This is particularly so with respect to' the use of mixing valves 'with four cycle engines of smrall size, which are used as utility power sounces on lawnmowers, outboard motors, etc. Four cycle engines normally have two operating speeds: a low speed or idlin'g operation an'd a high speed operation in which the speed is controlled or 'governed by any appropriate means.

Mixing vaives normally have a single control or adjustment forboth high and low speeds of the engine. Because of this arrangement, it 'is necessary that the low speed operation of the engine be under conditions at which a maximum amount of fuel or a rich air-fuel mixture is introduced into the engine. This is necessary so that at high speeds when a greater .amount of air enters the mixing conduit there will be suflicient fuel mixed' with the air 'to provide proper operation -for high speed. Thelevel of fuel in the tank also laifects the not only suflicient fuell flow at high speeds but also at 6 a very low level of fuel in the fuel tank. This necessity of utilizing a very rich mixture for low speed engine operation results in a rough running engine at this speed and a'very inefticient operation of` the engine because of the excessive use of fuel. This operation of a mix'ing valve also results in excessive use of fuel and thus poor efficiency at high speeds, when the fuel tank is full. v

lt is therefore an object of this invention to provide 'a novel mixing valve 'or carburetor -for a four cycle engine which has a minimum of adjustrnents and is of low cost and yet which operates efliciently 'at 'low speeds.

It is another object of the invention to provide a novel mixing valve or carburetor in which low speed operation is eflicient.

It is a further object of this invention to provide a novel mixing valve or canburetor for a four cycle engine which has la proven efficiency `an'd economy at both low and high speeds of operation.

It is another object of this invention to provide a novel mixing valve or ca-rburetor for internal combnstion engine in which low cost fabrication is obtained having required tolerances -to the economy of engine operation.

The invention is one which is disclosed as being inv corporated in a m-ixing valve |for internal combustion engines of the four cycle type to enable the engine to op-er-ate at 'a maximum economy at both low and 'high speeds. It is necessary to provide a source of ,air to mix with the excessive use of fuel during low speed operation. This is done by the use of a single aidjustable control for the flow of fuel through the suction tube to the mixing conduit. fDuring high speed operation, the fuel from the suction tube is emitted through nozzle ljets in 'a restricted area of the mixing conduit as well as through a low lVelocity metering jet za'djacent to the throttle. During low speed operation, however, the high speed meten'ng jets in the nozzle are -utilized to bleed air into the fuel circuit to provide a thinner air-fuel mixture for low speed operation. p

The mixir'ig valve itse'lf is made of sheet metal parts, tub-ular and drawn, which are loeked together by a bolt assembily. The par-ts provide fuel passages for the fuel circuits; the high speed fuel circuit being within the bolt assembly, while the lowl speed fuel circuit formed in one of the drawn meta'l parts. This type of construction is both economical and low cost in fabrication yet provides the required tolerances for effective operation of the mixing valve for the purposes desired.

FIGURE 1 is a top plan view partially of an engine and' 'its fuel tank together with the mixing valve, in accordance with this invention.

FIGURE 2 is an elevational view in section along lines 2- 2 of FIGURE '1.

FIGURE 3 is an elevational view in section 'along lines 3-3 of lFIGURE 1.

FIGURE 4 is 1a top plan view of the cover plate used in the device of the invention in FIGURE 1.

FIGURE 5 is a top plan view of the gasket usediin the device of the invention in FIGURE 1. j

FIGURE 6 is a sectional view in elevation of 'a modifi'cation' of the invention.

FIGURE 7 is |a sectional view along lines 7-7 of 5 FIGURE 6.

`l'IGURE 1 :discloses .an assembly of an engine E covered by a shroud 11, to the manifold M of which is fixed a mixing valve 9. A fuel tank 13 is also connected to the assembly and to the rnxing valve 9. The engine E is not a part of this invention and may be of any well known -conventiorral two cycle or four cycle type. The fuel tank 13 is attachezd to the engine and the mixing valve 9 is supported between the engine and the top of the fuel tank. Fuel tank '13` is of any well known type and consists of a metal tank having a screw cap 15 for the introduction of fuel therein.

In accordance with the invention, and as shown in the figures of the 'drawing the mixing valve consists of a tubular mixture conduit structure 14), formed of a sheet metal tube of uniform `diameter having a straight portion 12 at one end and a curved portion 14 at the other end (FIGURE 1). A flange 16 is fixed to the Curved end 14 of the mixture conduit and provides a means for attaching the mixing valve to the manifold M of the engine. Attachment may be in any appropriate mian'ner 'as by nuts 18 threaded onto studs, for example, extending through fiange V16 land threaded into the rn'anifold M. The other end of the mixture conduit 10 is fixed to an air filter housin'g 20, which consists of a re'ctangular metal b-ox structure made of sheet metal of which one side 22 comprises a 'detachable metal plate and a cover. for the air filter. The air filter structure 21B has a central portion drawn out into a cylindrical collar 24 which forms a press fitting onto the tubuliar end of the conduit portion 12, as shown in FIGURES 1 and 2, for example. The cover plate 22 of the air filter housing 20 is formed with 'a pair of longitudinal fiange members 26 which fit over the side w'alls of the box structure 2d and in which are small indentations 28 for fitting into apertures through the side walls of the box structure 20 to form a means for detachably fastening the cover plate 22 to the air filter housing structure.

Within the cover plate 22 are formed longitudinal louvers 32 which are bent inwardly and provide openings through the cover for 'air entering the mixture conduit '10. Also, the ends of the air filter housing 20 are open for the aidrnission of air into the housing. The housing itself is filled with -an air filtering material 34, such as sp'un glass or a Sponge plastic material, through which air may pass and the idirt particles therein filtered out. The air lilter material 34 is formed in the shape of a rectangular block which fits snuigly into the box structure of the 'air filter 20.

Fixed to the bottonr of the straight tubular portion 12 of mixture conduit'ltl, there is a cover plate 36 made of sheet metal iand drawn to form a 'semi-cylindrical upper surface 38, into which the niixing conduit portion 12 is fitted. Between the cover plate 36 and the conduit portion 12 is a fuel resistant 'gasket 40 'for preventing fuel leakage between the cover plate and the mixing conduit. FIGURE shows one form of gasket 46.

A bolt assembly 42 is used for holding and fixing the mixture conduit rigidly to the cover plate 35. Bolt 'assembly 42 includes a drilled bolt 44' having an axial passage 45 therethrough 'and a redu'ced end portion 48 'forming a shoulder 46 with -the other portion of the bolt. Bolt 44 passes through aligned apertures in the upper and lower surfaces 'of the conduit portion 12 'with the shoulder 46 in' contact with the inner surface of conduit portion 12. The lower end 48 of the bolt is threaded and has screwed thereon [a fuel metering nut '5d with the cover plate 36 between the nut 5d and the lower surface of conduit portion 12. That is, the cover plate 36 has a central 'aperture 52 (FIGURE 4) having a diameter equalt'o the outside diameter of the threaded portion 43 of bolt 44. As the metering nut 5h is threaded onto the end l1118 of bolt 44, it forces the cover plate 36 against the conduit portiou 12 vvith the gasket 4dtherebetween. Tightening of metering nut 50 brings shonlder 46 tightly down upon the inner surface of conduit portion 12 and forces the cover plate 36 against the under surface of conduit portion 12 so that the mixture conduit 1h is locked within the semi-cylindrical surface 38 of the cover plate 3d.

The metering nut 50 is 'formed with an axial passage therethrough having a restriction 54. A fuel metering adjustment screw So is threaded at its upper end and screwed into the internally threaded upper end of bolt 44. The metering adjustment screw 56 has a tapered lower end portion 58, which is adapted to extend through the restricted p'assage portion llin nut 51B so that the `relative positioning of ltapered screw end 5% within restriction 54 controls the amount of fuel fiow through the metering nut 51B.

Press-fitted into the lower end of the fuel metering nut Sll is a standpipe assembly 59 consisting of a hollow suction tube 57 having, press-fitted to its lower end, a fiared inlet element' Fixed across the fiared end of inlet element 6d is a metal mesh screen 61. Press-fitted within the lower end of the suction tube 57 'is a valve seat eyelet 62 upon which rests, by gravity, :a small ball valve 64. The suction tube 57 is formed with an indentaton 66 to prevent the ball 64 from escaping when the mixing valve is turned over.

The bolt assembly 42 and its 'clamping function with metering nut 50 is described and claimed in the copending application of Ott et al., fileid July 7, l1961, Serial Number 122,573.

The cover plate 36- is used to mount the mixing valve structure 9 ionto the fuel tank 13. The standpi-pe assernbly 59 is fitted 'downwardly through an aperture 68 in the |upper wall of the fuel tank. The standpipe assembly 59 is constructed so that the fiared 'bottom portion 60 is positioned adjacent to the bottom of the fuel tank v'13 and preferaibly over a shallow sump porion 70 in the bottom of the fuel tank. A gasket 72 between the cover plate 36 'and the top surface of the fuel tank prevents the escape of fuel between the cover plate and |the upper surface of the fuel tank. Fastening means such as screw bolts 74 are used for t'ightlyV attaching the cover plate 36 to the top yof 'the fuel tank and with the gasket 72 therebetween.

The unthreaded portion of the adjustment screw'56 has an outside diameter less than the diairneter of the passage 45 drilled axially through the bolt 44, and as shown in FIGURES 2 and 3, for example. This permits a suflicient lclearance between the 'metering screw 56 and the inner surface of passage 45 -to provide a fuel passage extending axially through the bolt 44. Ports 76 are formed through the bolt substantially normal to the axial passage through the bolt. These ports 76 connect the central region of the mixture conduit portion 12 with the axial bolt passage 45. The ports 76 may be four in number and lead outwardly at 90-from each other and from 'the passage 4-5. The ports 76 are positioned substantially on a common plane through the aXis of the mixture conduit portion 12 and normal to the axis of bolt' 44. lAn additional series of ports 78 are similarly formed in the lower end 48 of bolt 4-4. These ports 78 extend outwardly from the axial passage '45 and into a fuel and air mixing Chamber 80 formed between gasket 40 and lthe upper surface of the cover plate 3d which is drawn with a depression 81 in the semi-cylindrical surface 38 forming the lower portion of mixing Chamber 80, as shown in FIGURES 2, 3 and 4. A small aperture 82 is carefully formed as :a low speed metering jet through the bottom surface of the mixture conduit portion 12 so that it extends into the mixing Chamber 80. An enlarged aperture 84 through the gasket 401 enables the passage of a fuel and air `mixture from mixing Chamber 80 into the mixtnre conduit 12 through the metering jet 82. The diameter of the metering jet 82 is in the order of 0.030 in one carburetor of the type described.

The portion of bolt 44 extending through the mixture conduit portion 12 has a eylindrical 'outer surface, and

as indcated in FIGURE 3, forms a restriction. Air fiowing axially through conduit passes this restriction with I a higher Velocity to provide sub-atmospheric air pressure 'at the ports 76.

A choke valve 86 is mounted `on a choke valve shaft 88v journaled through appropriate apertures in the conduit portion 12 between -the air filter 20 and the upper end of bolt 44. One end of the choke shaft 88 is bent over to form a choke opera-ting lever 90'. The 'choke valve 86 itself is an elliptical piece of metal having a transverse axis a little greater than the diarneter of the conduit portion 12, and a conjugate axis substantially equal to the diameter of conduit portion 12. Thus, the choke valve 86, upon being turned from its opened position, shown in FIGURE 2, to a closed position,'will abut against the wall of the tubular conduit portion 12, which provides 'a stop means for the choke valve.

A throttle valve 92 is appropr-iately mountcd for rotational movement within conduit portion 12 on a throttle shaft 94, which is journaled at .one end in a recess 96 drawn out of the bottom wall of conduit por-tion 12 and at the other end in an aperture through the upper wall of the conduit portion 12. Shaf-t 94 is bent over to form van Operating lever 98 to provide rotational movement to the throttle 92. Throttle valve 92 is formed in a manner lsimilar to choke valve 86 with an elliptical configuration so that the wall of conduit portion 12 provides a stop means for the throttle, whenrotated to its closed position, as shown in FIGURE 1.

In operation, air sucked into the-manifold M of the engine is pulled through the air filter material 34 and through the mixture conduit 10.` During normal operation of the engine, the choke valve 86 is normally in a wide open position, as indicated in FIGURE 2. Also, the throttle 92 is between a paitially open to Wide open position. Thus, air can fiow through 'the carburetor and the conduit 10' into the manifold M;

As mentioned above, air flowing through the conduit portion 12 is forced into the restricted regions between the upper portion of b'olt 44 and the inner surface of the wall of conduit portion 12, which provide a venturi efiect as the fiow of air is speeded up' around the surface of bolt portion 44 with a resulting sub-atmospheric pressure in these regions. This sub-atmospheric pressure condition causes a fiow of fuel under atmospheric pressure from the 'tank 13 through into the flared end of standpipe assembly 59 into the suction tube 57, upwardly through the metering restriction 54, into the bo'lt passage 45 and out of ports 76. The ports 76, pointed upstream of the air flow through conduit 10, will permit some air to fiow into the upper end of passage 45 to mix with the fuel and pass out ofthe downstream passages as a mixture of fuel and air. The needle 56 is adjusted within restriction 54 to provide the desired amount of fuel for part throttle and wide open throttle conditions of operation.

For low speed operation, the throttle 92 is normally closed or nearly closed. The high vacuum provided on the 'downstream side of throttle 92 is suflicient to suck fuel from tank 13 through the standpipe assembly 59, ports 78, mixing Chamber 80 and out the low speed jet 82. Also, during this low speed operation, additional 'air is brought into the low speed circuit through ports 76 Upstream of the closed throttle 92. Air flowing through ports 76' will pass through passage 45 intothe mixing Chamber 80 Where it Will combine and mix with fuel brought in from the standpipe assembly 59.

' The adjustment needle 56 is positioned within the lrestriction 54 for an optimum high speed operation, when there is a maximum amount of air flow through conduit. 10. This adjustment, however, will provide an excessive amount of fuel fiow into the mixing Chamber 80 during the low speed and closed throttle operation of the mixing. valve. Thus, in accordance withthe invention, as described above, additional air is bled through ports 76 into the mixing chamber during low speed operation to provide a thinning of the enriched mixture; This additional -air fiow through ports 76 during low speed pro-p vides 'a greater economy in the operation of the engine during low speeds, as well as providing a smoother operation of the engine at these speeds, which is not possible with a highly enriched fuel-air rniXture.

In going from low speed 'to high speed, the throttle 92 is opened to par-t open or even wide open throttle depending upon the engine load. In the transition from closed throttle to open throttle the air flow past the ports 76 increases from vsubstantially zero to -an optimum amount. Also, the flow of fuel and air through lthe low speed jet 82 lessens as 'the engine manifold pressure drops with the opening of the throttle. Du'ring this transition period then, air' will cease to fiow 'through ports 76 into the passage 45 and mixing chamber 80 and rather fuel will be `sucked upwardly through passage 45 to the ports 76. H'owever, even during wide open throttle there is always some fuel flowing out the jet 82, due to the sub-atmospheric pressure in the manifold during this operation. The ports 76 thus have the dual function of providing main nozzle apertures 'for the emission of fuel, during open throttle operation and then providing air bleed ports into the passage 45 and mixing chamber 80 during low speed operation.

Mounted on the bolt 44 is a guard plate v100, through i which the threaded top ofthe fuel adjusting needle 56 extends and receives a lock-nut 104. In assembling the guard plate to the carburetor structure, an ear or L- shaped tab 106 (FIGURE 2) at the end of plate 100' is positioned within a slot in the upper side Wall of the air filter housing 20, ,and then plate 100 is brought down onto the top of bolt 44. Needle 56 is then inserted through an aperture in plate 100 and threaded into the upper portion of Ibolt 44. Nut 104 is threaded onto the upper portion of needle 56 and is tightened down to force plate 100 against the end of bolt 44.

A control lever structure 108 is rotatably journaled on the part of boltV 44 extending adjacent to plate 100. A coil spring 110, between lever 108 and conduit portion 12 presses the control lever 108 up-wardly againstjthe control plate 100. A dimple 112 (FIGURE 2) is struck up- Wardly 'out of the upper surface .of control lever 108 tO cooperate with apertures 114 ;andf116 formed in the con-V trol plate 100 (FIGURE 1). Under action of the spring 110, dimple 112 will ride' into the apertures 114 and 116 as the control lever 108 is rotated from one position to another.V The control lever 108 has several Operating arms or extensions for controlling operation of the carburetor.. One arm 118 (FIGURE 3-), extends downwardlyfrom the upper surface of lever 108. A ooil spring 120 has one end attached to lever 'arm 118 and the other end attached to the throttle control lever 98.. A second arml 122 of control lever 108. (FIGURE 1) has an aperture, to which is attached one end of a Bowden cable 124, for

- Operating the control lever 108 from a 'distance.

. The control unit shown and including the control ylever structure is described and claimed in the above mentioned applicationto Ott` et al.V

'Spring v`110 has one end- 126 fixed into' an aperture in conduit portion 12, as shown in FIGURE 2. The other end of. spring 110 consists of a straight section 128 extending from the bolt 44 into an aperture formed in the choke control lever 90.

The throttle valve 92of the carburetor is also controlled by a governor device, comprising an air fan on the fly wheel of the engine to blow air against a vane v130 pivotally mounted on the engine E. A rod 132 connects throttle lever, 98 to va'ne 1310 for the governor-control ofl the carburetor throttle.

1In the operation of the engine and motor, the starting of the motor may take place by closng the vchoke valve 86. 'Ihs is done bypmoving thecontrol Vlever 108 to-its farthest counterclockwise position, as viewedl in FIGURE 1. This may be done manually or by the Bowden cable 124. The lower lever arm 118 isthus forced against the straight portion 128 of spring 110, which rotates the choke lever 90 counterclockwise, as viewed in FGURE 1, to position the choke valve in a closed position. This closed position of the choke valve providesV su'fiicient air flow through conduit 10 for starting of the engine, 'but also insures an enriched fuel-air mixture for starting. The control lever 108, in this choking position, also holds the throttle valve in a wide open position by its connection to the throttle lever 98 through arm 118 and spring 120. The throttle is thus held opened against any bias tending to close the throttle, which may be exerted by the governor control.

Upon the starting of the engine, the control lever is then moved clockwise, as viewed in FIGURE 1, into the first intermediate position, in which the dimple 112 rides into aperture 116. In this first intermediate position, the throttle' valve 92 is still held in an open position. High speed operation of the engine will cause the engine governor through wire 132 and throttle lever 98 to move throttle 92 to a more closed position against the bias of spring 120. The movement of the control lever 108 from its choke or start position to the first intermediate position, as describedabove, allows the lever arm 118 to release the end 128 of spring'11i0, which swings the choke lever 90 clockwise, as viewed in FIGURE 1, to a ,full

open position against a stop 134 struck out of the upper i surface of plate '100. The choke is retained by spring 110 in this full open position during the other control positions of lever 108.

Movement of the control lever 108 to the second intermediate position, in which the dimple 112 rides into the aperture 114, closes throttle 92, since the spring 120 'becomes a rigid connector between the control lever arm 118 and the throttle lever 98. This is the low speed or idle position of the engine and with the throttle closed, insuflicient air passes through conduit 10 to operate the high speed or main fuel system in which fuel flows through the outlet ports 76. The low speed operation of the carburetor is as vdescribed above, Vin which the fuel is drawn through the idle jet 82.

`Movement of the control lever 103 to the farthest clockwise position, as shown in FIGURE 1, holds the throttle 92 inits closed position and in some modifications, one of thev arms of control lever 108 may contact an electrically live terminal of the engine ignition system to ground the ignition system and stop the engine.

fThe novel dependent fuel system described above and shown in FIGURES 1 through 5, may be utilized and adapted for use in a car-buretor. Such a modification is shown in FIGURES 6 and 7 in which the structures identical to those in FIGURES 1 through are indicated by the same reference numbers. The cover plate 36 of the first modification is now replaced lby a fuel bowl cover 136 having a top surface drawn :into configurations similar to that of the cover plate 36. For example, the fuel bowl cover 136 -is formed 'with shoulder portions 138 forming a semicylindrical surface in which the conduit portion 12 is mounted in the manner described above for the modification of FIGURES 1 through 5. Attached to the fuel bowl cover is a fuel bowl 140 which is utilized to provide a fuel reservoir for the carburetor. The 'bolt 44 is identical to that described above, however, the fuel metering nut is of a different form and consists of an elongated fitting 139 having at its upper end the restriction 142,`similar to restriction 54 of the first modification.' The fuel metering nut 139 is threaded onto the lower end 48 of bolt 44 to fiX the fuel bowl cover 136 against the mixture conduit portion 12 with shoulder 46 bearing against the inner surface of mixture conduit 12. 'I'he lower end of the fuel metering fitting 139 has a bore 143 which is internally threaded at the end thereof to receive a nut 144.

In assembling the fuel bowl to the fuel metering fitting 139, the fuel bowl is fitted onto the end of fitting 139. The lnut '1441 with a fuel resistant gasket is passed through 'the aperture in the bottom of the bowl 140 and tightened to force the upper edge of bowl 140 against a fuel resistant gasket 146 fitted between the bowl 140 and the fuel bowl cover 136. The fuel flows from fuel bowl 140 into bore143 of metering nut 139 through transverse apertures 141 in the wall of bore 143. The use of a fuel bowl alleviates the ditficulty of a variable fuel level in the fuel reservoir, which is characteristic of the mixing valve described in FIGURES 1 through 5. Accordingly, within the fuel bowl 140 there is placed a float 148 which is connected to an Operating lever for opening and closing an inlet valve to the bowl 140. This particular arrangement is well known and may be of conventional design, such as shown in the copending application to Ott and Hennemann, filed March 20, 1961, Aapplication Serial Number 97,007.

To provide a betterpcontrol of low speed operation and for idling, an idle port 150 -is formed through the wall of mixture conduit portion 12 upstream of the throttle valve 92, and as shown in FIGURE 7. The fuel bowl cover 136, as shown in FIGURE 7, is provided with a pressed or drawn indentation 152 extending into the mixing chamber 154 formed between the fuel bowl cover 136 and the mixture conduit portion 12-. The mixing charnber 154 corresponds to mixing chamber 80 of the mixing valve describediabove. An aperture 156 is formed in a gasket 158 corresponding to gasket 40 of the mixing valve described above, This arrangement, during the closed throttle operation of the carburetor, permits air Upstream o-f the throttle to pass through port 150 and channel 152 into the mixing chamber 154, so that there is an additional amount of air bled into the mixing chamber to that air bled into the low speed circuit through the fuel nozzles 176. As the throttle valve 92 opens, it will pass over aperture 150 so as to block ofi the air bleeding through this idle port, and upon further opening of throttle 92, it will pass 'beyond and Upstream of the idle port 150 so as to place this aperture 150 in contact With thevacuum of the engine intake 'manifoldv Thus, during the opening interim of the throttle 92, the idle port 150 ceases to bleed air into the mixture chamber 154 and then, as the aperture becomes downstream of throttle 92, it 'becomes a port for the passage of fuel out of the chamber 154 into the mixing conduit. l

V,A further control of the low speed or idle mixture through jet 82 may be obtained 'by the use of an idle adjustment screw'160, which is threaded through the upper wall of rnixing Chamber portion 12, and has a sharply tapered end extending into the idle jet opening 82. Adjustment of the idle screw 160 provides the Optimum amount of air fuel mixture passing through the idle jet 82 'for the Optimum operation of the engine at low speeds. The provision of the idle adjusting screw 160` permits a lower idling speed for the engine. Low engine speed using a metering valve of the type of FIGURES 1 to 5 is in the order of 1500 to 1600 r.p'.m., while with the adjustment screw 160, the idle speed of the engine can be adjusted to something Within the range of 900 to 1200 r.p.m.

'The invention provides means which permits a less rich, low speed operation of an engine resulting in better fuel economy, as well as a smoother running engine in this speed range. The use of the high speed nozzle to bleed air into the low speed circuit provides this improved low speed engine operation and makes engine operation less critical to fuel level in the fuel tank.

yThe structure described provides a low-cost mixing valve, in which low speed operation is greatly improved with no additional controls. The structure is fabricated from easily formed sheet metal parts which can be kept within reasonable tolerances to provide the desired engine operation.

We claim:

1. An air fuel mixture device comprising a tubular sheet metal body having a mixing conduit therethrough, a tubular bolt having an aXial passage therein and positioned within said tubular body transversely to said mixture conduit, a separate metal plate fixed to one side of said tubular 'body and 'forming a chamber therewith, and a gasket -between said metal plate and said tubular body providing a fuel-tight seal for said chamber, said bolt including a portion extending into said chamber, said bolt having a first and a second passage extending from said axial passage thereof into said mixture conduit and into said chamber respectively, said tubular ibody having an idle orifice through the wall thereof from said chamber into said mixture conduit.

'2. An air fuel mixture device comprising a tubular body having a miXing conduit therethrough, a throttle valve movably mounted within said mixture conduit, a tubular bolt having an aXial passage therein and 'positioned 'within and transversely through said mixture conduit upstream of said throttle valve, a metal plate having a surface portion fiXed adjacent to one side of said tubular body and formed with a depression in said surface portion, and a gasket between said plate surface portion and said tubular body providing a fuel-tight seal for said depression, said bolt including a portion extending into said plate depression, said bolt having a plurality of passages extending from said axial passage thereof into said mixture conduit and into said plate depression respectively, said tubular body having an idle orifice through the wall thereof extending from said plate depression into said mixture conduit downstream of said throttle valve.

3. An air fuel mixture device comprising a tubular sheet metal 'body having a mixing conduit therethrough, a throttle valve mounted within said mixture conduit for movement between open and closed positions, a tubular bolt having an axial passage 'therein and extending through said mixture conduit upstream of said throttle valve and substantially normal to the axis of said conduit, a metal plate having a surface fixed to one side of said tubular body, said plate surface having a depression therein forming a chamber with said body, and a gasket between said metal plate surface and said body providing a fuel-tight seal for said chamber, said bolt including a portion eX- tending into said chamber, said bolt having a plurality of ports extending from said aXial passage, a first one of said ports extending into said mixture conduit, a second one of said ports extending into said chamber, a third one of said ports adapted to' be connected to a source of fuel, means adjustably positioned within said third one of said ports to control fuel flow through said third pont, said tubular body having an idle port through the wall thereof and extending from said chamber into said mixture conduit downstream of said throttle valve.

4. The invention of claim 3 including a fuel reservoir,

having an opening in the top portion thereof, said metal plate fixed to said reservoir and covering said reservoir opening, said tubular member having an open end terminating in said reservoir and connected to said axial bolt passage.

5. The invention of claim 3 Wherein said tubular body has an idle air orifice through the wall thereof and eX- tending from said chamber into said mixture conduit upstream' of and adjacent to said throttle valve in closed position.

16. An 'air fuel mixture device comprising a tubular metal body having a mixture conduit therethrough, a throttle valve movably mounted within said mixture conduit, a tubular bolt having an axial passage therethrough and positioned through said tubular body and said mixture conduit upstream of said throttle valve and substantially normal to the axis of said mixture conduit, a metal plate having a surface fixed against the outer surface of said tubular body, said plate surface having a depression therein forming a chamber with said outer body surface,

a gasket -between said plate surface and said body surface providing a fuel-tight seal for said chamber, said bolt including a portion extending into said chamber, said bolt having a plurality of ports extending from said axial passage, a first one of said ports extending into said mixture conduit, a' second one of said ports extending into said chamber, a third one of said ports adapted to be connected to a source of fuel, and a rod element having a tapered end adjustably mounted Within said axial bolt passage and having said tapered end positioned within said third one of said ports to control fuel flow therethrough, said tubular bo-dy having an idle port through the wall thereof and extending from said chamber into said rnixture conduit downstream of said throttle valve.

7. An air fuel mixtnre device comprising 'a cylindrical metal body having a mixing conduit therethrough, a throttle valve mounted within said mixture conduit for movement between open and lclosed positions, a tubular member having an axial passage therethrough and positioned l'through said mixture conduit upstream of said throttle valve and transversely to said conduit, a metal plate having a semi-cylindrical surface receiving a portion of said cylindrical body, said plate surface having a depression therein forming a chamber with said cylindrical body portion, and a gasket between said plate surface and said cylindrical body portion providing a fuel-tight seal for said chamber, said tubular member including a section extending through said chamber and terminating in an open end adapted to be connected to a 'fuel source, said tubular member formed with a plurality of ports extending from said axial passage thereof into said mixture conduit and into said chamber respectively, said cylindrical body having an idle port through the wall thereof |and extending into said mixture conduit downstream of said throttle valve.

S. An air fuel mixture device comprising a tubular metal body having a mixing conduit therethrough, a throttle valve movably mounted within said mixture conduit, a tubular member having an aXial passage therethrough and positioned through said mixture conduit upstream of said throttle valve and transversely to said conduit, a fuel bowl, a fuel bowl cover plate closing said fuel bowl, said cover plate having a rounded surface receiving a portion -of said tubular metal body, said cover plate surface having a depression therein forming a chamber with said body portion, a gasket between said cover plate surface and said body portion providing a fuel-tight seal for said chamber, said tubular member including a section extending through said chamber and said cover plate and terminating in said fuel bowl, said tubular member formed with a plurality of ports extending from said aXial passage thereof into said mixture conduit and into said chamber respectively, said body having an idle port through the wall thereof and extending from said chamber into said mixture conduit downstream of said throttle valve.

9. An air fuel mixture device comprising a thin Walled tubular metal body having a mixing conduit therethrough, a throttle valve mounted within said mixture conduit for movement between an opened and a closed position, a tubular member having an aX'ial passage therein and positioned through said mixture conduit upstream of said throttle valve and transversely to said conduit, a metal plate having an arcuate surface receiving a portion of said tubular body, said arcuate plate surface having a depression therein forming' a chamber with said body portion, a gasket |between said metal plate surface and said body portion providing a fuel-tight Seal lfor said chamber, said tubular member including a section extending into said chamber and formed With 'a plural'ity of ports extending from said axial passage thereof, a first one of said ports extending into said mixture conduit, a second one of Said ports adapted to be connected to a source of fuel, a third one of said ports formed between said first and said second ports and extending into said chamber, said 'body having an idle orifice through the wall thereof and extending from said `Chamber into said miXture conduit ldownstream of said throttle valve and an iclle port through the Wall thereof extending from said Chamber into said mixture conduit upstrearn of said throttle valve When in a closed position, a rod element having a tapered end adjustably mounted within said tubular bolt -passage With said tapered end thereof positioned Within said second one of said ports to control fuel fiow therethrough.

References Citerl in the file of this patent UNITED STATES PATENTS Coulombe Jan. 29,

Alexandrescu Jan. 17,

Phillips Oct. 20,

FOREIGN PATENTS Germany Mar. 4, 

1. AN AIR FUEL MIXTURE DEVICE COMPRISING A TUBULAR SHEET METAL BODY HAVING A MIXING CONDUIT THERETHROUH, A TUBULAR BOLT HAVING AN AXIAL PASSAGE THEREIN AND POSITIONED WITHIN SAID TUBULAR BODY TRANSVERSELY TO SAID MIXTURE CONDUIT, A SEPARATE METAL PLATE FIXED TO ONE SIDE OF SAID TUBULAR BODY AND FORMING A CHAMBER THEREWITH, AND A GASKET BETWEEN SAID METAL PLATE AND SAID TUBULAR BODY PROVIDING A GUEL-TIGHT SEAL FOR SAID CHAMBER, SAID BOLT INCLUDING A PORTION EXTENDING INTO SAID CHAMBER, SAID BOLT HAVING A FIRST AND A SECOND PASSSAGE EXTENDING FROM SAID AXIAL PASSAGE THEREOF INTO SAID MIXTURE CONDUIT AND INTO SAID CHAMBER RESPECTIVELY, SAID TUBULR DODY HAVING AN 